Near-Infrared Optical Illumination for Injection Locking in Quantum Cascade Lasers

Since their first demonstration in 1994 [1], quantum cascade lasers (QCL) have shown great potential for many applications and more recently, it was also demonstrated that QCLs can generate frequency combs in the mid-infrared (MIR) [2]. Comb generation directly in the MIR is not trivial [3], and this spectral region is usually reached by nonlinear frequency conversion of lasers operating in the near-infrared (NIR). Hence using QCLs is advantageous especially considering their low footprint and high optical power properties. While QCL combs are routinely used in free-running states, stabilization of one or both comb degrees of freedom is necessary to harness the full potential of QCL as frequency combs. It was recently achieved by optical injection [4], or stabilization to a molecular reference [5].